Induction coil with split flexible insulating flange



July 24, 1962 o. R. wuczKowsKl INDUCTION COIL. WITH SPLIT FLEXIBLE INSULATING FLANGE Filed Nov. 9, 1959 ATTORNEYS.

United States Patent .0

' 3,046,509 INDUCTION COIL WITH SPLIT FLEXELE INSULATING FLANGE n Othmar R. Wuczkowski, Chicago, Ill., assignor to Lindberg Engineering Company, Chicago, Ill., a corporation of Illinois Filed Nov. 9, 1959, Ser. No. 851,748

3 Claims. l (Cl. 336-207) This invention relates to induction coil and method of j is wound helically 'with the conductor.

making the same and more particularly to the manufac-A ture and construction of large/high amperage induction coils for use in billet heaters and the like. Induction coils for billet heater-s Aand similar uses have generally been formed bywinding a relatively large copper conductor which is formed with passages therethrough for eirculation of cooling water into a helix and inserting arcuate segments of insulating material between the turns ofthe conductor as it is wound. After winding, the turns are compressed axially and lcovered or coated with yresinous plastic material to `serve as an insulating covering and as a binder.

This operation is diicult and laborious since the insulat ing segments comprising one turn or Vless must be inserted manually between lthe turns of the conductor as it is wound. It is very. difficult to get the insulating segments placed uniformly in this operation. Furthermore, in coating the assembly with resinous plastic binder it is ditiicult to get the binder into the coil between the turns thereof, which is `desirable to hold the turns together.

It is one of the objects of .the present invention to provide an induction coil in which the insulation between turns of the conductor is in the form of a continuous strip wound at the same time as the conductor.

Another object is to provide an induction coil and method of making the same in which the insulation is in the form of an L-section strip having one flange radially underlying the conductor and forming a tubular insulating liner 4for the coil and its other Iflange extending radially between adjacent turns of the conductor.

According to a feature of the invention, the radial flange of the insulating strip is slit at spaced points so that when the strip is wound the slits open into V-shaped slots to receive the plastic binder and permit it to penetrate the full thickness of the coil.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawings, in which:

FIGURE l is a partial perspective View of a wound coil prior to coating with plastic binder and with the coil cut and shown in section;

`FIGURE. 2 is a view looking -into one of the turnsof insulating material in the coil showing the plastic binder in place; t

FIGURE 3 is a partial section on the line 3-3 of FIGURE 2;

FIGURE 4 is a diagrammatic view illustrating thewinding the coil; and

FIGURE 5 is a sectional view illustrating the step of compressing the turns of thev coil.

A completed induction coil, according to the present invention, is formed by an electrical conductor 10, preferably of copper, wound into a tight helix with insulation between adjacent turns and lining the inner surfacethe present invention and it will be understood that any desired type of conductor may be employed.

The turns of the conductor .are insulated from each otherby means of an insulating strip, indicated generally at 13, which is L-shaped in cross section and which y The insulating strip includes an axially extending ange 14 which radially underlies the conductor in the completed coil with Ithe .turns of the flanges 14 substantially in contact with each other to form a continuous .tubular insulating liner for the coil. A second ange 15 of the insulating strip extends radially between adjacent turns of the coil to separate them from each other. In order to permit bending of the flange 15, it is formed throughout its length with spaced slits 16 which will Iopen up as the strip is Y wound todene V-shaped open slots 17. The ilange 15 is preferably of slightly greater width than the conductor so' that in the completed coil it will project beyond the conductor as shown.

In forming the coil, the conductor 10 and the insulating strip 13 may be simultaneously wound on` a cylindrical mandrel, as indicated in FIGURE 4, over which an insulating sleeve 18 may be fitted, if desired. The conductor and insulating strip .are fed simultaneously onto the mandrel in the manner illustrated in FIGURE 4 with the conductor overlying the axial flange 14 of the insulating strip and with the radial flange 15 of the insulating strip being wound between adjacent turns'of the conductor. It will be noted that this operation can be performed as la continuous 'winding operation with no necessity lfor any manual steps being performed simultaneously with the winding.

As the conductor and insulating strip arejwound, the slits 16 inthe liange 15 will open up to define the V-shaped slots 17 in the manner more particularly illustrated in FIGURES l and 2.

After the conductor and insulating strip have been wound into a helix of the desired length, the adjacent turns are preferably compressed axially in the manner shown in FIGURE 5. As illustrated in this figure, the turns which lie around the sleeve 18 are engaged at their opposite ends by annular plates 19 which may be drawn together axially by bolts 21 to press the turns of the conductor and insulating material tightly against each other.

While the turns of the coil are held in compressed condition a resinous plastic binder, such as an epoxy resin, is applied thereto. This may be `done by brushing, spraying, dipping or in any other desired manner to pro'- vide an insulating covering over the conductor and to bind the turns of the conductor together. As will be seen in FIGURES 2 and 3, the resinous material indicated at 22 will iiow into the open slots 17 to pene-w trate the full thickness of the coil. Preferably the material is applied in sufcient quantity to cover the outer surfaces 4of the conductor with a coating approximately one-eighth inch in thickness, valthough this is not critical. The resin may then be cured either by the 'application of heat or by air curing, depending upon the particular resin employed. When cured, the resin will adhere to the surfaces off the conductor and of the insulating material to secure them rigidly together in a unitary assembly. It will be noted that in addition to flowing into the slots 17, resin will ow to some extent between the surfaces of the conductor and the insulating material to form .a very Y 4tight bond resulting in a rigid assembly.

After curing of the resin, the coil may be lined or enclosed in any` other desired manner, as is known in the art, for mounting in apparatus such as a billet heater and may be used in the normal way. However, due -to the fact that the turns of the coil are rigidly secured vibration of the coil turns in response to the application of power thereto is minimized and a very efficient construction results which is at `the time relatively easy to form.

While one embodiment of ythe invention Ihas been shownand described herein, it willbe understood that it is illustrative only `and not to 'be taken as a vdefinition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

l. An induction coil comprising a conductor Wound into a helix With adjacent turns spaced apart and an insulating Vistrip L-shaped in cross section helically inter- Wound with the conductor Iwith one flange of the `strip lying radially within and contacting the inner surface ott the conductor land dening a tubular liner therefor and the other flange extending radially between -the turns of the conductor, said other ange being split radially at spaced points in the length of the strip.

2. An induction coil .comprising a conductor wound into a helix with adjacent turns spaced `apart and an insulating strip L-shaped in cross section helically interwound with the `conductor with one flange of the strip lying radially within and contacting the inner surface-of the conductor and dening a tubular liner therefor and` References Cited in the le of this patent UNITED STATES PATENTS 2,435,093 MitSChrich Jan. 27, 1948 2,455,355 Com-bs Dec. 7, 1948 2,471,777 Reinartz May 3l, 1949 2,735,075 Thomason Feb. 14, 1956 2,829,354 Sealey Apr. l, Y1958 Kuttner June 14, 1921 

